Frequency range converter



May 19, 1936. G. w. WALTON FREQUENCY RANGE CONVERTER Filed Aug. 8, 1932 5 Sheets-Sheet 1 T) g u 471% -o ooooood A d 1 L li m 5 1555. a

May 19, 1936.

G W. WALTON FREQUENCY RANGE CONVERTER Filed Aug. 8, 1932 '3 Sheets-Sheet 2 y 1936- G. w. WALTON 2,041,036

FREQUENCY RANGE CONVERTER Filed Au 8, 1932 5 Sheets-Sheet 3 Flllllllllllll 3 44 I Illllllllllll 5 3 #7 5:42 17 P 55% 45 T rr 1 Patented May 19, 1936 UNITED STATES FREQUENCY RANGE CONVERTER V 7 George William Walton, London, England Application August 8, 1932, Serial No. 627,963

In Great Britain December 1, 1931 8 Claims.

This invention relates to methods of and means for converting electrical oscillations of one range of frequencies into electrical oscillations of a second range of frequencies, the second range being a representative of the first range and being capable of substitution for that first range in any process of electrical practice. The invention is particularly but not exclusively concerned with electrical oscillations representing sound. The invention also provides means for the reconversion of the second range of frequencies into the original or into any other expanded range of frequencies.

Hitherto all known methods of transmitting sound by electrical means have used a range of electrical frequencies each of which corresponds exactly to a sound frequency, that is to say, if a sound is composed of four different frequencies, it has been represented by four electrical frequencies, each of which has the same frequency as the original sound. In such spheres as electrical transmission of sound, electrical recording and reproduction of sound and the like, very great difficulties have been experienced due to the fact that the range of sound frequencies which are audible to the human ear is very wide, ranging between twenty per second to twenty thousand per second approximately ten octaves. As a result of this, great difiiculties are experienced in telephones, wireless telephony, gramophones and the like. For instance in telephone lines of great length the cut off frequency is often not greater than between 2000 and 3000 cycles per second, so that a large portion of the sound frequency range is completely eliminated in transmission. This is a very serious difficulty and hitherto has been wholly insuperable. Again in wireless telephony, methods hitherto used have consisted of modulating a high frequency oscillation with sound frequencies, thereby producing side bands of the carrier oscillation, each of which side bands has a range of frequencies equal in width or frequency separation to that of the original band. The whole range of wireless frequencies necessary to transmit telephony has been about twenty kilocycles wide, with the result that only a very limited number of wireless stations may transmit simultaneously, because each station requires a separate band of frequencies, and the transmission bands of no two stations must be allowed to overlap, as otherwise serious interference with each other would result. In sound recording and reproducing great difiiculties have hitherto been experienced due to the inability of the recording apparatus to im press the highest frequencies on the record. For instance, in the gramophone plate record all frequencies above 6000 cycles per second are eliminated, i. e. a very large portion of the sound frequency range is removed. Further the material of the gramophone plate has usually a texture which makes it impossible to record the higher frequencies. In talking film sound records, diflicu'lty is experienced in recording the higher frequencies due to the size of the photographic 10 grain, the length of film available for the record, the speed at which it must be run, and the speed of response of the photographic emulsion to light.

The object of the present invention is to remove these difficulties in the spheres mentioned, and for this purpose entirely new methods and devices are provided.

The human car has a certain resolving power, that is to say, two adjacent sound frequencies must differ from each other by a certain per- 2 centage in wave length. In arriving at what this percentage is, account must be taken of present day music. In the western civilizations musical notes generally vary by half a tone, that is to say, there are not more than sixteen sound frequencies distinguishable in one octave. Oriental music on the other hand goes somewhat further than this, and quarter tones are made use of, so that there are not more than 32 sound frequencies in every octave. In general it is extremely diflicult for the average human ear to distinguish more than 64 distinct sound frequencies in every octave. From, this it will be appreciated that the resolving powers of the human ear are extremely limited;

In 7 electrical apparatus means are. known whereby frequencies much closer together can be distinguished and a resolution of about 5% between two frequencies can be readily obtained,. particularly when it is not required that those frequencies should actuate instruments, or be 40 isolated from each other.

It is well known to convert one range of frequencies into a different range of frequencies. For example in wireless telephom where acarrier of say a millon cycles per second is modulated by a band of sound frequencies extending from 30 to 10,000 cycles per second, one side band contains a band of frequencies extending from 1,000,030 to 1,010,000 cycles per second. But it will be noted that the band width or the separa+ tion between extreme frequencies in the band has remained unaltered; namely 99,970. Similarlyin heterodyning the band width remains unaffected.

The present invention provides means whereby one frequency of. a rangeof primary frequencies of primary frequencies mayralsorbeicontinuous.

' human ear, a discontinuous range of frequencies different from that of the primary range.

a A range of sound frequencies strictly speaking consists of a continuous range of frequencies,

that is to say an infinite number of different frequencies, but due to the poor resolution of the may be used, that is, a limited number of frequencies will be capable of representing sound for all practical purposes.

In this. invention both methods may be used,

i that is to say, the secondary, representative range of frequencies produced from a continuous range and have an infinite number of frequencies; Alternatively the second representative range may i consist of only a limited number of frequencies, 20

each primary frequency being: converted into the secondary frequency nearest to that which strictly corresponds to the primary frequency. Thus each secondary frequency is representative of a narrow'bandof primaryfrequencies. When such a secondary frequency range isreconverted into a normal. sound frequency-range, only an equal limited number of frequencies is present. In thissecond method strictly speaking, there will be sornechanges of frequencies, but each frequency of the original sound will be reproduced as a frequency very close to the original sound frequency, so'cl'ose indeed that the human car will be incapable of distinguishing any difference. The invention will be described with reference to the accompanying drawings-it being of course understoodthat these drawings are purely illustrative and that the invention is by no means limited to theparticular forms shown, but includes all arrangements within the scope of the appended claims;

In the drawinga: Figs. 1A and; 1B show diagrammatically, in" elevation and plan respective ly, one form of frequency range converter using threecoils, V V a Fig. 2 shows a diagram'of the circuits, connections and auxiliary device by means of. which deviceone is able to convert frequency ranges,

3' shows more fully the" connections and arrangement necessaryfor frequency range conversion, V V V Fig 4 shows an-alternati've form of' frequency range converter using ductor,

Figs. 5 to '7- show alternative forms of frequen'cy range converter, Fig.8 shows diagrammatically the connections two coils and one 'conof a frequency range converter for converting one modulated oscillation into-a second modulated oscillation, 1 a f V Fig. 9' shows a form of frequency range con- 'verter using one coil and two. conductors,

. Fig. 10jshows: a formof frequency range converter using two coils, Y I

I Fig: llshowsa diagram of connections of the device ,of Fig. 10, a

. l2.sh ows a further form of frequency range converter using one coil and one conductor,

= Fig. 13 shows a? form of frequencyrange converterfor very high frequencies using three conductors,

l Fig. 14 shows a form of frequency'range converter using one coil and one conductor, Fig} 15 shows an alternative form of Fig. 14,

" Fig. 16 shows a diagram of connections in which the whole of the frequency range conor' all anti-clockwise.

verter device is common to primary and secondary circuits,

Fig. 17 shows a double form of frequency range converter of the Fig. 15 type, and

Fig. 18 shows a diagram of connections using the device of Fig. 1'7.

In Fig. 1 an evacuated vessel I contains three coils 3, 4 and 5 supported by .apinch 2. One end of'each of the coils 3, 4 and 5 is connected to external circuits by means of the leads 6, I

and 8 respectively, which .pass through and are sealed into the pinch 2. The vessel I contains a 'gas such as neon, argon andthe like at a suitbe bare, at least at the points where the three coils are close together, namely. at 9: in, the cross sectional view B. 'I'hecoils 3', 4 and 5 should be wound in thesame direction, i. c. all clockwise Fig. '1 should be such that there is some lag in the action of the device, that is to say that'a glow discharge once established between the coils should not be immediately extinguished. when the'potential producing'it is removed, but the lag should in no case be longer than the time interval required by the human ear to detect a change in sound whichris believed to be' between one-sixteenth and one thirty-second of a second.

The device of Fig. 1 can be used to produce a discontinuous range of frequencies for example as shown in Fig; 2. I is a diagrammatic repre- It is desirable that the pressure and type of gasuused the device of sentation of the device of Fig; 1 with its three coils 3, 4 and 5 and leads 6, I and 8. The lead 6 is connected through a condenser III and an inductance II to the positive pole of the battery I2 across which is shunted a by-pass condenser I3. The, negative pole of the battery I2 is con-. nected bymeans of the lead I to the coil 4. The coil 5 is connected to the positive pole of the battery I2 through lead 8, co'ndenser I4 and coil I5. There are, therefore, two oscillatory circuits, the first containing coil 3, condenser I0, coil II and coil 4, and the second containing coil 5, condenser I4, coil I5- and coil 4. The battery I2 applies-to the device, such a potential that an electric discharge just cannot takeplacefrom coils 3 and 5 to coil 4.. When a discharge takes place at any point between coils '3 and 4, a connection is made between the coils atthis point and the firstcircuit will be tunedto a definite frequency which is thenatural frequency of the circuit comprising the inductance II, condenser .Ill and the parts of coils 3 and 4' between the Should As the coils 3, 4 and 5 have an equ'alnumber of turns, say 1000 each, then there will be in the .firs't circuit 1000,tuning points, and similarly there will be 1000 tuning points in the second circuit. If the coil I 6, which is coupled to coil II, is energized by a band of frequencies, the

first circuit will be energized at those fre-' quencies. Suppose that the range of applied frequencies is such that the first circuit resorepresentative of .the amplitude of each nates at the highest frequency of the range when a connection between coils 3 and 4 is made at a point where the whole of both coils are excluded from the tuned circuit, and that the circuit resonates at the lowest frequency of the band when connection is made between coils 3 and 4 at a point which includes the whole of those coils within the tuned circuit, then that circuit will be capable of responding to the whole range of frequencies, but the tuning of the circuit will only take place at 1000 points between coils 3 and 4.

For anyone frequency in the applied range, there will be some point of discharge along coil 3 to an opposite point on the coil 4 which offers the least impedance to the oscillation in the tuned circuit, and consequently discharge will take place at that point. Similarly every other frequency in the applied range of frequencies will cause a discharge at some corresponding point between coils 3 and 4, and more than one frequency may be present simultaneously, each producing its own discharge between coils 3 and 4.

When a discharge takes place between coils 3 and 4, there will be a cathode glow on coil 4 and as can be seen from the arrangement in Fig. 13, this will reduce the resistance to discharge between coils 5 and 4, thereby initiating a discharge between coils 5 and 4 at a point exactly opposite the discharge between coils 3 and 4, for the potential between coils 5 and 4 is such as to be just below striking voltage and therefore when the resistance to discharge between those coils is reduced, a discharge immediately takes place. It will, therefore, be appreciated that every discharge between coils 3 and 4 will produce a discharge between coils 4 and 5, and as the circuit containing coils 4 and 5 is also a tuned circuit, each discharge will set up in the second tuned circuit an oscillation of a frequency determined by the natural frequency of the circuit comprising the condenser I4, inductance I5 and those parts of the coils 4 and 5 between the discharge point and the leads 1 and 8. The range of frequencies applied through coil [5 will therefore produce in the second tuned circuit a corresponding range of frequencies which may be withdrawn through coil I'I.

If condensers I0 and [4 are equal, and coils II and 15 are equal, then the range of frequencies in coil I! will be the same as the range of fre quencies in coil I6, with the difference that there will be only 1000 distinct frequencies in coil l1.

If coil II has a different inductance from coil 15, then the range of frequencies in coil I! will be entirely different from the range of frequencies in coil I6. The former range will still be the range in coil [6, but the representation will be only by 1000 separate frequencies, each corresponding to a small range of frequencies within the range in coil l6, and frequency in coil l1, will correspond to the amplitude of the frequency it represents in coil l6, because an increase of amplitude of one frequency in coil 16 will produce a more intense discharge between coils 3 and 4 thereby producing a lower resistance to discharge between coils 4 and 5. For example, suppose the range of frequencies in coil 16 is one side band of a sound modulated oscillation, say 1,000,032 to 1,016,384. cycles per second, and'suppose that the circuit containing-coils 3 and 4 has such constants that the frequency 1,016,384'pro duces a discharge between .coils ,13 and 4, at a taneously without interference.

point'which cuts out the whole of coils 3 and 4 from the tuned circuit and that the frequency 1,000,032 produces a discharge between coils 3 and 4 at a point which cuts in the whole of coils 3 and 4. If the coil l5 and the condenser 14 are of such values that a discharge between coils 4 and 5 which cuts out the whole of coils 4 and 5 from the tuned circuit produces a frequency of 1,000,032 cycles per second and a discharge between coils 4 and 5 which cuts in the whole of coils 4 and 5 produces a frequency of 1,000,128, then in the circuit containing coil II we have a frequency range from 32 to 16,385 plus 10 cycles per second, and in the circuit containing coil l5 there is a frequency range from 32 to 128 plus 10 cycles per second; Thus the second range corresponds exactlyto the first range of frequencies but is considerably narrower. By heterodyning the oscillations in coil I! with a carrier oscillation of one million per second and rectifying, a range of low frequencies from 32 to 128 cycles per second will be obtained, and this range will represent the range of sound frequencies from 32 to 16,384 cycles per second which were used to produce the frequencies in coil l6 by modulating an oscillation of one million per second, i. e. a sound range of nine octaves is represented by two octaves, resulting in a compression to about one-fifth of the range. If necessary, increased lag of the device of Fig. 1 can be obtained by connecting an inductance in series with the battery 12 in Fig. 2, so that the by-pass condenser I3 is shunted across both the battery and the inductance.

The advantages obtained from this compression of frequency band in ordinary line telephony are firstly that it is possible to transmit perfect telephony over the longest lines and even submarine cable without any essential frequency being eliminated or reduced, secondly extreme care in the arrangement of the constants of the transmission lines becomes unnecessary, that is,

loading coils and the like are unnecessary, thirdly over one telephone line several telephonic cornmunications may take place simultaneously withent for the whole transmission band will be only 256 cycles wide, thereby enabling increased selectivity in receivers, improved efliciency of transmitters and receivers, and an increase of the number of stations which may transmit simul- In sound recording and reproduction, equal advantages are obtained. A gramophone record will be able to accommodate a much longer record, and at the same time perfect sound will be recorded up to the highest audible frequencies and in talking films similar advantages may be obtained.

, Many other arrangements may be used to obtain similar effects. For instance in the circuit including coil 3 in Fig. 2, both the side bands and the carrier of a modulated oscillation may be applied, so that for every frequency in the hand there is a corresponding discharge point along coil 3 and the circuit containing coil 5 may have such constants that an entirely different band of frequencies is produced in the circuit by discharges from coil'3 to coil 4. This derived band of frequencies may have an entirely different carrier frequency, but nevertheless there .willbe an effective narrowing of the modulating 1 'condensersare chosenL" l r r The'second representative range of frequencies aqua-1a, band if: suitable. values or cells and as above described, i. e. 32-to I28:cycles persecond, may be used for all purposes connected with transmission, reception, recording and reproduction of oscillations in just the same way'as the original sound frequency range of 32 to 16,384, but iwith all the advantages previously described. It is only necessary that after these various processes have been accomplished, the two 'ocjtave range shall be re-converted into a blue octave range by the arrangement of Fig. 2 or one similar to it. ,Obviously, there-conversioninvolves exactly the same process *as that previouslydescribed, 'exceptfthat it is arranged; to produce an expanded range instead of a contracted range of frequencies. 7 H

c Fig. g shows a circuit arrangement which may be usedto obtain a frequency range conversion.

The device of Fig; 1 is used as in Fig. 2, and

an inductance illis arranged in series with the battery'IZ as previously described. An oscillating triode 19 has its tuned circuit 20' coupled to the grid circuit of the triode 2i and a transformer '22 is also included in. the grid circuit and is fed through terminals 23 with any range of frequencies. In coil l6 there appears a modulated oscillation which energizes the tuned circuit.

of coil 3 as before, thereby producing in the circult of coil a second rangeof frequencies which are applied tothe rectifyingtriode 24 through the coil l1 in itsgrid circuit, A coil 25 coupled to the tuned circuit 20' also supplies to the triode 24 the carrier oscillation which is rectified to: gether with the range of frequencies from the circuit of 'coil5 bymeans of the leaky grid con-- denserrzfi and the triode 24 whilst the, anode circuit of the triode 24 maybe coupled'to the grid circuit thereof as shown to. increase the output. The low frequency oscillations produced by rectification in the 'triode 2 4 are passed by transformer 21 to the secondary output terminalsill. One anode battery l2 supplies, potentialsito all the triodes as wen as to the device I and one filament heating battery 29 supplies current to. all the filaments of the triodes. The

' 1 arrangement of :Fig. '3 may. be 'used for a contraction of a frequency range as well as for an expansion thereof, 'i. e. reconversion. Many suitable circuit arrangements may beused other than that of Fig. 3and are all within the scope of the invention, the essential device of any such arrangement being that of Fig. 1 or any equivalents thereof such for example as are herein described v In the device of Fig. 1 the coil'4 may be re placed by a plain conductor as shown'for example in Fig. 4, Where 30 is a straight conductor such as a metallic wire, supported between the pinch 2 and an insulating support 32. Connected' to the conductor 30 is a lead 3| which passes through and is sealed in the pinch 2. The device of Fig. 4 operates in exactly thesame way r as the device of Fig. 1 and is connected to circuitsiin exactly the, same way, the lead 3lof Fig. '4 being'connectedin' the same Way as lead f Fig.1;

Insorne cases it is necessary that the limited numberof frequencies to.which the devlceof Figs. 1 and 4 can respond shouldfollow some more complex law, for instance the output frequencies may be arranged as a harmonic scale preferably equilateral.

r or there maybe aconstant difference of fre- V quency or any other suitable variation as de- .siredJForthis' purpose thecoils 3'and 5, and t in some case's 'the coil 4 also, of Fig. 1 may be so constructed the inductance of successive turns of the coils changes along the length of the coil.: This may readily be accomplished by arranging that the former on which the coil is wound varies in cross-sectional area along its.

'takes place between the coils they should preferablybeparallel, so that the resistance of the discharge path is constant throughout the length ofthecoil as otherwise the amplitudes of the frequehcle's'of the second range will not be proportional to those of the actuating frequencies. This point is not essential, for in'some cases it maybe desirable that the amplitude of some frequencies shall be reduced relative to others, for instance, low frequencies ".may' have correspondingly lower amplitudes than thehigher frequencies, and vice versa in order to compensate for the characteristics of some of the devices handling thesefrequencies. The devices of Figs. 5 and '6 may also be of thetype 'shown'in Fig. 4,

ple conductor.

It will be noted that the devices of-Figs. 1, 4; 5 j

and cant not only'tocut out or cut in inductance but also to vary the capacity between ,theturns of adjacentcoils and in the use of these devices for any particular purpose this inter-coil capacity must betaken into account as it obviously plays some part in the tuning of the circuits. 7

In the designing of the devices of Figs. 1, 4, 5, and 6, it is preferable that the from a coil should be along a defined line and to obtain this the former on which the, coil is wound may have a sharp ridge forming something like aknife edge over which the turns of "the coil are wound asshown at 9 in Fig. 7 and at points of discharge 9 in Fig. 1B. The'ridges of the coils are arranged path of dischargebetweenany two coils as shown at 9 in Fig. 1B, where the ridges of the three coils are disposed at the corners of a triangle, which is In the case of the. device of Fig. 4, the ridges of the two coils maybe at two corners of a triangle and the conductor 30 at the thir'd corner of the triangle. By arranging the device in. this way,

Fig. 4 will be such as to cause a definite reduction of the resistance of thedischarge pathbetween by rectification as in normal wireless practice.. 7 r

This method is not very. desirable in wireless transmission as the single side band without carrier wave is diflicult to receive. This is be.- cause the local carrier oscillationat the receiver is likely to be very unstable, and'to be continually changing its phase The carrier oscillation in so as toconstitute. the boundaries of the shortest I v v t the glow discharge on the cathode,- i. e.jcoil 4 in Fig. 1 and conductor 30 in be'in the-for m of one side band without car- 7 coil I 6 of Fig. 2 may however be transmitted with the range of frequencies from coil I! in Fig. 2, but even this is not as stable as is desirable and one side band only of the carrier does not allow the use of extremely selective circuits at the receiver. It is therefore desirable that the transmission should be in the form of a carrier oscillation with two side bands. Oscillations of this character-can be obtained, as already described, by applying a carrier oscillation with both side bands to the coil I6 in Fig. 2. This method is however not entirely satisfactory because the lowest frequency of the contracted transmission band appearing in coil I! would be less than 16 per second and as this is greater than the smallest time interval in which the human car can detecta change of sound, diificulties may be experienced.

A better 'method is shown in Fig. 8, where instead of the device of Fig. 1 a special type of device is used, in which the coils are each in two sections, 3 and 3a, 5 and'5u, and in which an inductance 33 connects the-two halves 3 and. 3a together whilst an inductance 34 connects the two halves 5 and 5a together. The value of the inductance 33 is made such that the higher of the two sides frequencies corresponding to the lowest modulation frequency will cause a discharge from the upper end of coil '3 and the lower of the two side frequencies corresponding to, this same modulation frequency will cause a discharge from the lower end of coil 3a. In general the lowest modulation frequency will be higher than per second. Similarly the value of the inductance 34 is arranged so that the lowest modulation frequency'appearing in the contracted range of frequencies is also greater than 20 .per second. This is done by arranging that the differencebetween the resonant frequency when only the coil5 is in circuit with the half of coil 4 and the resonant frequency when both coil 5 and coil 34 'are in circuit therewith is greater than 40 cycles.

it will be seen that frequencies below the lowest which it is desired to convert require a tapping to be made somewhere in coil 33 to produce resonance and these frequencies therefore cause a discharge to pass across the gap between discharge points 35 and. 31. This discharge reduces the resistance between points 36 and 31 and initiates in the second circuit an oscillation having a resonant frequency equal to that of the second circuit 'with the whole of coil 5 and one half of coil 34 in circuit with the half of coil 4. The range of frequencies in the circuit of coil 5 may be used for transmission or reception purposes in the same way as in normal wireless communication and extreme selectivity will be obtainable. At the receiver, conversion may be obtained by using the arrangement of Fig. 8.

Another method of wireless transmission and reception using the invention. which is compara tively simple, consists in converting the sound frequency range into a second range of half the width, that is to say, each primary frequency appears at half the frequency in the secondary range. The secondary range is thus used to modulate the carrier oscillation and before transmission the constant carrier oscillation is eliminated by any of the known methods, so that only the side bands are transmitted. At the receiver the side bands alone are received, and a local oscillation equal in frequency to the original carrier oscillation is not used. Consequently reception is obtained by the heterodyning of pairsofside frequencies. Each pair of side frequencies gives rise on heterodyning and detection to a frequency vantages of this method are that normal wireless receivers may be used and the'frequency range converter need only be used at the transmitter.

Moreover the actual transmission band is only one half the width of that which'is produced by using the original sound frequencies :for modulating purposes.

Fig. 9 shows a type of device using 'only one coil and two conductors and it may be regarded as the converse of Fig. 4. The conductor 38 takes the place of the coil '3 of Fig. 1 and the conductor 3% the place of coil 5 inFig. 1 and. conductors 3S and 39 supported between members .2 .and 32. The connections of the device'in use :are exactly the same as those 'shown'in Fig. 2. The'coil 4 when connected'in the circuit is obviously common to both primary :and se'condary tuned circuits,:just as coil 4 of the device of :Fig. 1 isccommon 'to both tuned circuits, for the action "of'the device is practically the same.

It is possible to use a device coils 3 and 5 as shown in Fig. '10, connections being made to both ends of each coil, leads 42 and 43 connecting with the upper ends 'of coils 3 and 5 and leads 6 and 8 connecting with the lower which it will be seen that a portion of each of the coils 3 and 5 is included both :in the primary and in that the highest frequency of the primary range of frequencies will produce the' lowest fre quency in the secondary ranged-frequencies, and vice versa, but in practice this is usually of no im por'tance for the secondary range is completely representative of the primary range. 7

An alternative formo'f device to th t shownin Fig. 10 is shown in Fig.12 where only one coil 3 is used, having connections 'to both ends, together with a conductor 39. The device -'of 12 is connected into the circuit as shown in Fig. 11', the conductor 39 taking thep'lace of coil. 5 in that figure. This device has the same character I istics as the device-of Fig; 10.

The frequency range converting devices previously described have all'been of the type which produces a discontinuous range of frequencies.

but it is possible to obtain acontinuous rangeof frequencies by using the device shown in 13. In this case the conductor 38 corresponds to coil 3 in the device of Fig. 1, the conductor 30 to coil 4, and the conductor 39 to coil 5. Theconductors 38, 33 and 39 are supported between the pinch 2 and an insulating support 32 and are enclosed in an evacuated vessel in which there is a gas at suitable pressure, so that an electric discharge can takeplace'between the conductors. The leads 43, 3| and 4| are connected to one end of the conductors '38. 30 and39 respectively, and external circuits similar to those "shown in Fig. 2 may be used. The frequencies of the applied oscillations must in this case be very high, in order that. conductors 38, 33 and '39 shall not be too long.

As described in connection with Fig. 2,'for each.

of the applied frequencies there will be a point along the conductor 38 at which one frequency will discharge to an opposite point of the conductor 33, thereby establishing a discharge between conductors 30 and 39. at the same point topro- 7 ends thereof respectively. "Theconnectionsof the device when in circuit are shown in Fig. 11 from duce another frequency in the-secondarycircuit;

In this case portions of the conductors ,38 iand' 30 willbe' brought into circuit by the discharge, and

thesev portions have electrical constants of such a vial'ue that the primary circuit is tuned to the actuating frequency and similarly portions of the conductors 30'a'nd 39 are brought into the secondary circuit to tune that circuit to some; corresponding frequency' A portion'of the capacity between'the'conductors 30 and 39 is brought; into circuit'as'well as the inductance thereof and this also afiects the tuning of the primary'circuit. Similarly a portion of the capacity between the conductors 30 and 39 is brought into the secondary circuitfas well as aiportion of their inductance. Practically the length of theconductors 3 8, 30 and 39 is limited, and therefore a practical form of the device" of Fig. 9 can onlyrbe used with'thewery highest frequencies.

I Thelimitations 'of the device of Fig. 13 can'be overcome by using the device of Fig. 14.

' losses," and'it may be "constructed of magnetic In Fig..14 the coil 3 is wound on the inside of an insulating former 44 and conduc'tor 30 passes through the centre. of the coil coincident with the axis. Connections of the device in use are simi- .larto those of Fig. 12, and. its action is that a discharge'can take placefrom any point of the coil material for the purpose of reducing'eddy'current wouldbe so small as to be negligible.

losses withinits mass, although generally these 15 shows an'alternative form operating in the same way as the device shown in Fig. 14, except that'in this case coil 3 is wound on the outside of the former 44 and surrounding it and concentric with 3 but not making contact therewith is an pen endedcyIinder 45 (shown cut away in Fig. 15'to expose coil 3 and former v44) which acts 'as a conductor to which the coil 3 can discharge;

The cylinder 45'should preferablybe constructed of magnetic material having low magnetic losses and high electrical resistance in order to reduce the eddy current losses to a minimum. Connec- V tion is made to'the cylinder'45 by mean s'of the lead 46 and the connections of the device when in circuit are similar to the devices of Figs. 12

and 14; The cylinder .45 instead of being closed may also have a longitudinal slit to prevent the circulation of short circuit currents'induced 'in it by the coil 3.

V Devices according to Figs. 10, 12, 14 arid 15 may be used with only two connections to the'device,

'forinstance in- Fig.10 connections 6' and 8, in

Fig. 12 connections 6 and 4|, in Fig. 14 connections '6 and 3|, and. in Fig; 15 connections 6 and 4,6, but in these cases a different type of circuit 7 V 7 must be used, in which the inductance of the frequency range converting device is common to both primary and secondary circuits. One 'such arrangement is shown in Fig. 16, in which it will be seen that the coils.3 and 5 of the device of Fig.;10 are common" to both the primary. circuit and the secondary circuit, the source of potential 12 and a choke l8 being shunted across the coils V 3 and 5.- The device of Fig. 13 with only two conductors 38 and 39 may be used alsoin the arrangement of Fig. 16 V i The primary circuit in the arrangement of Figs. 2, 3, 11 and 16 actuates the frequency range.

converter in half-cycles, that is to say the fre- ,.q uency range converter acts'asa rectifier of the oscillations in the primary circuit, there being other.

no discharge in thefrequen'cy range converter during the negative half cycles, consequentl'y'the primary current through the device is in thenature of isolated impulses, i. e. the positive half cycles, and in the arrangement of Figs."3, 11 and 16the inductance 3 tends to maintain a con- .stant primary current flowing through thefre quency range converter, which constant current,

is approximately at the mean level'of theim- The more constant'the' primary current through V n the device, the better will e the oscillation produced in the" secondary circui'hand for this rea-' son twodevices; or a double device may be used so as to obtain thefull wave rectification of the primary oscillation, which will obviously result in' a more constant oscillation in the secondary circuit. Further disadvantages of the arrange ments shown in Figs. 2; 3, 11 a'nd16 are that primary frequenciesmay be induced in the sec ondary' circuit by inductive, capacitative and conductive coupling, and for this reason it is generally preferable that the rangeof frequencies in' the secondary circuit shall-be completely outside the tuning range of the primary circuit and vice versa, in order that secondary frequencies induced in the primarycircuit shall not set up new primary oscillations capable of actuating the" frequency range converter. Otherwise one primary frequency will set up in the secondary circuit a different frequency which will appear, due to the coupling, in the primary circuit and will inturn produce another secondary frequency, and so on, until each primary frequency will have produced a very large number of secondary frequencies. These difliculties can also be obviated by the use of a' double device, and a suitable type is shown in Fig. 17 which may be con sidered as a'double device of a type similar to that shown in Fig. 15.

In Fig. 17 there are mounted at right angles to one another'two coils 3 and 3a supported by the supports 48 and 48arespectively, one end of each coil being connected to external. circuits" by means of the leads 6 and'lia'respe'ctively. Around each of these coils and concentric therewith is.

disposed an open-ended conductingcylinder, the

. cylinder '45 being arranged around coil 3 and the cylinder 45aaround coil3a. Thesetwo cylinders are. connected together and supported by the supports 41 and both are connected to the external circuit by means of the lead 46. All the supports are mounted in the pinch 2 so that the various parts are'held in a rigid relation to each The two coils are mounted at right angles in order that they shall not have appreciable mutual inductance. The use of the device is shown in Fig. 18.

In Fig. 18 the double device represented by the coils 3 and 3a and the conductors 45 and 45a are connected as shown, one end of a coil l5 being connected to the middle point of a coil ll. Consequently the primary circuit, which consists of .coil 1 l, condenser 49, coil 3, conductor 45, con

ductor'45a,lcoil 3a and condenser 49a, may be regarded as a double circuit, each half being equal, the first half being half of coil ll, condenser'49, coil 3, conductor 45, condenser I 3 and inductance l5, and from the primary circuit point half circuits, the frequency range converter will full wave rectify the primary oscillations. The

secondary circuit consists of'condenser l3, coil l5, and then branches into two parallel circuits, one consisting of half 'of coil H, condenser 49a, coil 3 and conductor 45, and the other c onsisting of half of coil ll, condenser 49a, coil 3a and conductor 4511. Consequently the primary frequencies in coil 15 are rectified, and therefore cannot appear in coil I1, and the secondary frequencies in coil I E travel in different directions in the two halves of the coil, therefore balance out in the primary circuit. From this it will be seen that primary and secondary frequencies are incapable of interfering with each other, as the circuit is a kind of bridge circuit.

In Figs. 3, 11, 16 and 18 the secondary oscillation will commence as soon as the primary actuating oscillation commences to be rectified in the primary range converter, but if that device has a lag, there will be a slight delayed action. Similarly when the primary oscillation ceases'the secondary oscillation also ceases sometime later, depending on the lag. In order that the secondary oscillation may be constant, it is possible to apply reaction to the secondary circuit, for instance in Fig. 3 the anode coil of the triode 24 may be coupled to the inductance l5, but the amount of reaction must not be so great as to produce a constant oscillation, for should this be so the oscillation will persist after the primary actuating oscillation has ceased. By varying the amount of reaction it is also possible to produce the effect of lag in the frequency range converter.

In the devices of this invention it is preferable that the electric discharge between the electrodes shall be confined as much as possible, and for this purpose the coils used in the device may be Wound in groups, the coils being so mounted that the formers touch or are very close together. In this way the discharge is confined to one group. Alternatively, separators may be placed between adjacent turns of the coils and between the coils for the same purpose.

Many other forms of device and circuit arrangements for frequency range conversion are possible within the scope of this invention, the essential feature of a frequency range converter being that each primary oscillation shall support a secondary oscillation of adifferent frequency, and that all the primary oscillations in a band shall simultaneously be able to produce corresponding secondary oscillations.

I claim:

1. Apparatus for converting electrical oscillations of a primary range of frequencies into electrical oscillations of a secondary range of frequencies different from said primary range, said apparatus comprising two resonant circuits capable of resonating over different frequency ranges, means for impressing electrical oscillations upon one of said circuits and means whereby the effective resonant frequency of the other of said circuits is determined by the frequency of the oscillations in said first circuit.

2. Apparatus for converting electrical oscillations of a primary range of frequencies into electrical oscillations of a secondary range of frequencies different from said primary range, said apparatus comprising two resonant circuits capable of resonating over different frequency ranges, means for impressing electrical oscillations upon one of said circuits and means whereby the effective resonant frequency of the other of said circuits is changed in steps as the frequency of the oscillations applied to said first circuit is changed.

3. Apparatus'for converging electrical oscillations of a primary range of frequencies into electrical oscillations of a secondary range of frequencies, said apparatus comprising a glow discharge device, two impedance elementslocated within said device and constituting electrodes thereof, a first resonant circuit including one of said impedance elements, a second resonant cir-' cuit including the other of said impedance elements, means for applying oscillations of said primary range to said first circuit to produce a glow discharge in said device and means for deriving oscillations of said secondary range from said second circuit.

4. Apparatus for converting electrical oscillations of a primary range of frequencies into electrical oscillations of a secondary range of frequencies, said apparatus comprising a glow dis charge device, two impedance elements located within said device to constitute electrodes thereof and having an elongated discharge space of substantially uniform width between them, a first resonant circuit including one of said impedance elements, a second resonant circuit including the other of said impedance elements, means for applying oscillations of said primary range to said first circuit to produce a glow discharge in said device and means for deriving oscillations of said secondary range from said second circuit.

5. Apparatus for converting electrical oscillations of a primary range of frequencies into electrical oscillations of a secondary range of frequencies, said apparatus comprising a glow discharge device, two impedance elements located within said device to constitute electrodes thereof and having an elongated discharge space of substantially uniform width between them, a first resonant circuit including one of said impedance elements, a second resonant circuit including the other of said impedance elements, means whereby a glow discharge in said discharge space serves to tune one of said circuits to one frequency and the other of said circuits to a different frequency, means for applying oscillations of said primary range to said first circuit to produce a glow discharge in said device and means for deriving oscillations of said secondary range from said second circuit.

6. Apparatus for converting electrical oscillations of a primary range of frequencies into electrical oscillations of a secondary range of frequencies, said apparatus comprising a glow discharge device, an impedance element located within said device and constituting an electrode thereof, two additional electrodes within said device, two resonant circuits each including the said impedance element, means for applying oscillations of said primary range to one of said circuits to produce a glow discharge in said device and means for deriving oscillations of said secondary range from said second circuit.

'7. Apparatus for converting electrical oscillations of a primary range. of frequencies into electrical oscillations of a secondary range of frequencies, said apparatus comprising a glow discharge device, an impedance element located within said device and constituting an electrode thereof, two additional electrodes within said device, two resonant circuits each including the said impedance element, means whereby a glow discharge in said device serves totune one of said circuits 'to :one frequency and the other 01 said circuits to a different frequency. means for applying oscillations of said primary rangekto rone. 5: of said circuits to produce .a glow dischar e in said device and means .for ==deriving oscillations "of said secondary range from said second circuit.

- 8; Apparatus for converting electrical :oscillations of a primary range ofrirequencies into elecm'tricai oscillations of a secondary rangeof frequencies; said apparatus comprising a glow discharge device, an impedance element located a 1 acumen within said deviceVandiconstituting an electrode thereof, two additional electrodes within said de vice having between them-and said impedance element an elongated dischargespace 01 substantially uniform width, two resonant circuits each including the said impedance element, means for applying oscillations of said 'primary range to one of said circuits to produce a glow discharge in said discharges-space and means for deriving oscillations of said secondary range from said 19 second circuit. l V

' GEORGE WILLIAM WALTON. 

